Among elements which belong to the group 16 of the periodic table, five elements including oxygen (O), sulfur (S), selenium (Se), tellurium (Te) and polonium (Po) are referred to as oxygen group elements and, of five, only three elements of sulfur, selenium and tellurium are referred to as sulfur group elements or chalcogens.
Oxygen and sulfur are representative non-metal elements, whereas other metals lose non-metallic properties and increase in metallic properties as atomic number increases. Selenium, tellurium and polonium are rare elements, whereas polonium is a naturally radioactive element.
Metal chalcogenide is a compound of a transition metal and chalcogen, which is a nano material having a similar structure to graphene. Metal chalcogenide has a very small thickness corresponding to a thickness of an atomic scale layer, is thus soft and transparent and has electrical properties such as semiconductor and conductor properties.
In particular, metal chalcogenide having semiconductor properties has a suitable band gap and electron mobility of hundreds of cm2/V·s, thus being applicable to semiconductor devices such as transistors and having great potential as elastic transistor devices.
MoS2, WS2 and the like, which are metal chalcogenide materials on which the most active research is conducted, are capable of efficiently absorbing light due to direct band gap under a single layer condition and is thus suitable for application to optical devices such as optical sensors and solar cells.
A method of producing a metal chalcogenide nano thin film has been actively researched. However, there is a need for requirements of metal chalcogenide thin films for application to the devices, that is, methods of uniformly and continuously synthesizing large-area thin films.